Cover member for a magnetically operated clutch

ABSTRACT

An electromagnetic clutch is disposed between a drive source and a driven device for connecting and disconnecting the drive source to and from the driven device, respectively. The electromagnetic clutch includes a body rotatable by the rotative power from the drive source and an armature faced to, but normally spaced from the rotatable body. An exciting solenoid when energized moves the armature into an engaging position where the armature is attracted and urges against an end face of the rotatable body. A bearing is disposed between a fixed member of the driven device and the inner peripheral surface of the rotatable body for rotatably supporting the rotatable body on the fixed member. A cylindrical cover member is fixedly mounted, independently of the bearing, on a portion of the inner peripheral surface of the rotatable body between an axial end face thereof and the bearing. The cover member includes a peripheral wall covering a gap between the rotatable body and the armature and an annular end wall extending radially inwardly from an axial end of the peripheral wall by a considerable distance and cooperating with the peripheral wall to define a reservoir for oil and grease.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electromagnetic clutch forrespectively connecting and disconnecting a drive source to and from adriven device having a fixed hollow cylindrical projection and arotatable shaft extending within the hollow projection in concentricrelation thereto. More particularly, the present invention relates to anelectromagnetic clutch suitable for use with a compressor used in anair-conditioning system installed on a motor vehicle, for example.

2. Description of the Prior Art

An electromagnetic clutch of the kind referred to above comprises arotatable body made of magnetizable material. The rotatable body isdisposed around a fixed hollow cylindrical projection of a drivendevice, such as a compressor for a cooler in concentric relation to thecylindrical projection and is drivingly connected to a drive source,such as an engine of a motor vehicle for rotation around an axis of ashaft of the driven device. The rotatable body has its inner peripheralsurface faced to the cylindrical projection and opposite axial endfaces. A bearing is disposed between the outer peripheral surface of thecylindrical projection and the inner peripheral surface of the rotatablebody for supporting the rotatable body on the cylindrical projection.

An armature made of magnetizable material and connected to the shaft forrotation therewith is faced to one of the opposite axial end faces ofthe rotatable body, but is normally spaced therefrom by a suitable gap.The armature is movable between an engaging position where the armatureis attracted and abuts against the one axial end face of the rotatablebody to allow the rotation of the rotatable body by the drive source tobe transmitted to the shaft and a disengaging position where thearmature is spaced from the one axial end face of the rotatable body bythe suitable gap to prevent the rotation of the rotatable body frombeing transmitted to the shaft. An exciting solenoid is associated withthe armature to move the same between the engaging and disengagingpositions in response to energization and deenergization of thesolenoid.

The rotatable body has formed on its inner peripheral surface an annularshoulder adjacent to the one axial end face of the body. In addition,the cylindrical projection of the driven device has formed in its outerperipheral surface an annular groove at a location substantiallyradially opposite to the annular shoulder. A cylindrical cover member isdisposed adjacent to the bearing for preventing leaked oil and greasefrom entering the gap between the armature and the one axial end face ofthe rotatable body. The cylindrical cover member includes a peripheralwall for covering the gap, and an annular end wall extending from anaxial end of the peripheral wall remote from the bearing and cooperatingwith the peripheral wall to define a reservoire for the leaked oil andgrease. The cylindrical cover member has an annular flared portionprojecting substantially radially outwardly from the other end of theperipheral wall of the cover member. Upon the assembly of theelectromagnetic clutch, the flared portion is clamped by and between theannular shoulder and an axial end of the bearing. Thus, the cylindricalcover member is fixedly mounted on the inner peripheral surface of therotatable body. Thereafter, a snap ring is caused to pass through anopening defined by the annular end wall of the cover member toward thebearing, and is fitted in or snapped into an annular groove in the outerperipheral surface of the cylindrical projection of the driven device sothat the bearing is held in position against axial movement.

With the prior art arrangement described above, the diameter of theopening defined by the annular end wall of the cylindrical cover memberis required to have a size sufficient to enable the snap ring to passthrough the opening. This makes it impossible to increase the radiallength of the annular end wall of the cover member. Accordingly, the oilreservoir defined by the peripheral wall and the annular end wall of thecylindrical cover member cannot receive therein a considerable amount ofoil and grease. In addition, in the case where the bearing has a smallradial dimension between the inner and outer peripheral surfaces of thebearing, it is difficult and troublesome to fit the snap ring into theannular groove, because the cylindrical cover member is previouslyinstalled and the snap ring is required to pass through the openingdefined by the annular end wall of the cover member.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an electromagneticclutch which facilitates the assembling operation, particularly, theattachment of the snap ring and which enables the reservoir for oil andgrease to have an increased volume.

According to the present invention, there is provided an electromagneticclutch for respectively connecting and disconnecting a drive source toand from a driven device having a fixed hollow cylindrical projectionand a rotatable shaft extending within the hollow projection inconcentric relation thereto, the electromagnetic clutch comprising: arotatable body made of magnetizable material and disposed around thehollow cylindrical projection of the driven device in concentricrelation thereto, the rotatable body being drivingly connectable to thedrive source for rotation around an axis of the shaft and having aninner peripheral surface faced to the cylindrical projection andopposite axial end faces; a bearing disposed between an outer peripheralsurface of the cylindrical projection and the inner peripheral surfaceof the rotatable body for rotatably supporting the rotatable body on thecylindrical projection; an armature made of magnetizable material andconnectable to the shaft of the driven device for rotation therewith,the armature being faced to one of the opposite axial end faces of therotatable body, but normally spaced therefrom by a suitable gap, thearmature being movable between an engaging position where the armatureis attracted and abuts against the one axial end face of the rotatablebody to allow the rotation of the rotatable body by the drive source tobe transmitted to the shaft and a disengaging position where thearmature is spaced from the one axial end face of the rotatable body bythe suitable gap to prevent the rotation of the rotatable body frombeing transmitted to the shaft; an exciting solenoid associated with thearmature for moving the same between the engaging and disengagingpositions in response to the energization and deenergization of thesolenoid; and a cylindrical cover member fixedly mounted, independentlyof the bearing, on a portion of the inner peripheral surface of therotatable body between the one axial end face thereof and the bearingfor covering the gap between the one axial end face of the rotatablebody and the armature, the cylindrical cover member having an annularend wall extending radially inwardly from an axial end of thecylindrical cover member remote from the bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an electromagnetic clutch inaccordance with an embodiment of the present invention; and

FIG. 2 is a view similar to FIG. 1, but showing the prior artelectromagnetic clutch discussed previously.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown an electromagnetic clutch inaccordance with an embodiment of the present invention which is appliedto a compressor 1 for a cooler used in motor vehicles and is generallydesignated by the reference character 10. The compressor 1 comprises afixed housing 2 having a hollow cylindrical projection 3 and a rotatableshaft 4 extending within the projection 3 in concentric relationthereto. More particularly, the electromagnetic clutch 10 in accordancewith the embodiment of the present invention shown in FIG. 1respectively connects and disconnects a drive source, such as an engine5 to and from the compressor 1 which is a driven device.

The electromagnetic clutch 10 includes a rotatable body 12 made ofmagnetizable material. The rotatable body 12 includes radially inner andouter peripheral walls 14 and 16 in concentric relation to the rotatableshaft 4 of the compressor 1, and an annular end wall 18 extendingbetween an axial end of the inner peripheral wall 14 and thecorresponding axial end of the outer peripheral wall 16 to define anannular recess in the rotatable body 12. An annular V-grooved member 20is fixedly mounted on the outer peripheral wall 16 in concentricrelation to the shaft 4 of the compressor 1. The V-grooved member 20 isconnected to a pulley 6 of the engine 5 through a V-belt 7 so that therotatable body 12 is continuously rotated around the shaft 4 of thecompressor 1 during the running of the engine 5.

A bearing 24 having inner and outer races 26 and 28 is disposed betweenthe outer peripheral surface of the cylindrical projection 3 on thehousing 2 of the compressor 1 and the inner peripheral surface of theinner peripheral wall 14 of the rotatable body 12 for rotatablysupporting the rotatable body 12 on the cylindrical projection 3. Moreparticularly, the inner race 26 of the bearing 24 has one axial endthereof abutting against a shoulder 30 on the outer peripheral surfaceof the cylindrical projection 3 and the other axial end abutting againsta snap ring 32 snapped into or fitted in an annular groove 34 formed inthe outer peripheral surface of the cylindrical projection 3. The outerrace 26 has one axial end thereof abutting against the snap ring 36fitted in an annular groove 38 formed in the inner peripheral surface ofthe inner peripheral wall 14 of the rotatable body 12 and the otheraxial end abutting against a shoulder 40 on the inner peripheral surfaceof the inner peripheral wall 14. Thus, the bearing 24 is held inposition against axial movement.

A ring-like armature 42 made of magnetizable material is connected tothe shaft 4 of the compressor 1 for rotation therewith, and is faced toan end face or attracting face 44 of the end wall 18 of the rotatablebody 12, but spaced therefrom through a suitable gap G. The armature 42is movable between an engaging position where the armature is attractedand abuts against the attracting face 44 of the rotatable body 12 toallow the rotation of the rotatable body 12 by the engine 5 to betrransmitted to the shaft 4 of the compressor 1 and a disengagingposition where the armature is spaced from the attracting face 44 by thegap G to prevent the rotation of the rotatable body 12 from beingtransmitted to the shaft 4.

A connecting mechanism 50 for connecting the armature 42 to the shaft 4of the compressor 1 for rotation therewith includes a ring 52 having aL-shaped cross-section and fixed to the armature 42 by rivets 54 at aplurality of circumferentially spaced locations. The connectingmechanism 50 further includes a hub 56 which has a cup-shaped bodyportion 58 and a hollow projecting portion 60 extending axially from thebottom of the cup-shaped body portion 58 toward the compressor 1. Theshaft 4 of the compressor 1 is received in the hollow projecting portion60 and has a free end face abutting against a circumferential projection62 formed on the inner peripheral surface of the hollow projectingportion. The shaft 4 is fixedly connected to the hollow projectingportion 60 of the hub 56 through a key 64 for rotation therewith. Inaddition, the hub 56 is fixed to the shaft 4 by a bolt 66 passingthrough an opening in the bottom of the hub 56 in communication with thehollow portion of the hollow projecting portion 60 and threadedlyengaged with the shaft 4 with a head of the bolt 66 abutting against thecircumferential projection 62. A cushion ring 68 made of resilientmaterial, such as rubber is positioned between the ring 52 and thecup-shaped body portion 58 of the hub 56 and is adhesively securedthereto. The cushion ring 68 has an annular portion positioned betweenthe ring 52 and cup-shaped body portion 58 and an annular portionpositioned between the armature 42 and the cup-shaped body portion 58.Because of the cushion ring made of resilient material, the connectingmechanism 50 connects the armature 42 and the shaft 4 to each other soas to allow the armature 42 to be rotated with the shaft 4 and alsoallow the armature 42 to move toward and away from the attracting face44 of the rotatable body 12.

A yoke 70 made of magnetizable material and having a generally U-shapedcross-section is concentrically disposed within the annular recessdefined by the inner and outer peripheral walls 14 and 16 and theannular end wall 18 of the rotatable body 12, and is welded to anannular plate 9 which is fixedly secured to the housing 2 of thecompressor 1. An annular solenoid 72 is concentrically disposed withinthe cylindrical yoke 70 and is located axially opposite to the armature42. An insulating ring 74 made of material such as epoxy resin andhaving a generally U-shaped cross-section is disposed between thesolenoid 72 and the yoke 70 to prevent the solenoid from being in directcontact with the yoke.

A cylindrical cover member 80 located adjacent to the axial end of thebearing 24 may be made of a material having resiliency, such as resin,iron sheet, hard rubber or the like. In the illustrated embodiment, thecover member 80 is made of 66-nylon. The cover member 80 has aperipheral wall 82, an annular projection 84 extending radiallyoutwardly from an axial end of the peripheral wall and an annular endwall 86 extending radially inwardly from the opposite axial end of theperipheral wall toward the outer peripheral surface of the projectingportion 60 of the hub 56 to define a central opening 88. The annularprojection 84 may be tapered or may have an arcuate cross-section tofacilitate the installation of the cover member 80. The annularprojection 84 of the cover member 80 is snapped into an annular groove90 formed in the inner peripheral surface of the inner peripheral wall14 of the rotatable body 12 so that the cover member 80 is fixed inposition. The annular groove 90 is located between and spaced from theattracting face 44 and the shoulder 40 against which the bearing 24abuts. Thus, the cover member 80 is fixedly mounted, independently ofthe bearing 24, on a portion of the inner peripheral surface of theinner peripheral wall 14 between the attracting face 44 and the bearing24. The peripheral wall 82 of the cover member 80 covers the innerperipheral edge of the gap G between the attracting face 44 of therotatable body 12 and the armature 42 to prevent the leaked oil flowingfrom the compressor 1 as indicated by an arrow 91 and the grease for thebearing 24 flowing as indicated by an arrow 92, from being introducedinto the gap G. It is desirable that the annular end wall 86 of thecover member 80 has its radial length h as long as possible. In otherwords, it is desirable that the opening 88 defined by the annular wall86 has its diameter as small is size as possible. The reason for this isthat the annular end wall 86 cooperates with the peripheral wall 82 todefine a reservoir for the leaked oil from the compressor 1 and thegrease for the bearing 24, and the annular end wall 86 having theincreased radial length enables the reservoir to have an increasedvolume.

The cylindrical cover member 80 is secured to the inner peripheral wall14 of the rotatable body 12, independently of the bearing 24. Thisenables the cover member 80 to be secured to the inner peripheral wall14 of the rotatable body 12, after the snap ring 32 has been snappedinto the annular groove 34. This, in turn, eliminates the necessity tocause the snap ring 32 to pass through the opening 88. Accordingly, itis possible to decrease the diameter size of the opening 88.

In operation, when an electric current is supplied to the excitingsolenoid 72, magnetic flux is produced as indicated by the dot-chainline MF. The armature 42 is moved into the engaging position where thearmature is attracted and abuts against the attracting face 44 of therotatable body 12. The power from the engine 5 is transmitted to theshaft 4 through the pulley 6, V-belt 7, rotatable body 12, armature 42,cushion ring 68 and hub 56 to rotate the shaft 4, thereby to actuate thecompressor 1.

When the exciting solenoid 72 is deenergized, the magnetic flux isextinguished, and the armature is moved to the disengaging position showin FIG. 1 under the resilient force of the cushion ring 68, todisconnect the compressor 1 from the engine 5, thereby to halt orsuspend the operation of the compressor 1.

The projection 90 of the cylindrical cover member 80 may becircumferentially continuous, or may be discontinuous. If the covermember 80 is made of an iron sheet material having low resiliency, theperipheral wall 82 may be provided with a plurality of radiallyoutwardly extending and circumferentially spaced lugs which are fittedin the annular groove 90, in place of the annular projection 84. Thecylindrical cover member 80 may be secured to the inner peripheralsurface of the inner peripheral wall 14 of the rotatable body 12 bymeans of knurling, adhesive bonding, welding or the like. In such case,the annular projection 84 may be unnecessary.

As described above, in the electromagnetic clutch in accordance with thepresent invention, since the cylindrical cover member 80 is fixedlymounted on the inner peripheral wall 14 independently of the bearing 24,it is possible to secure the cylindrical cover member 80 to the innerperipheral wall 14 of the rotatable body 12, after the snap ring 32 hasbeen snapped into the annular groove 34 to axially position the bearing24, upon the assembly of the electromagnetic clutch. In other words,upon the assembly of the clutch, it is not required to cause the snapring 32 to pass through the opening 88 defined by the annular end wall86. This enables the radial length h of the annular end wall 86 to beincreased, thereby to enable the oil reservoir defined by the annularend wall 86 and the peripheral wall 82 to have an increased volume. Inaddition, upon the assembly of the electromagnetic clutch, since thesnap ring 32 is snapped into the annular groove 34 prior to theinstallation of the cylindrical cover member 12, the snap ring can beeasily fitted in the annular groove 34, even if the bearing 24 has areduced radial dimension between the inner and outer peripheral surfacesof the bearing, i.e., even if the distance between the inner peripheralsurface of the inner peripheral wall 14 of the rotatable body 12 and theouter peripheral surface of the projection 3 on the housing 2 of thecompressor 1 is small.

FIG. 2 shows the prior art electromagnetic clutch similar to that of thepresent invention and discussed in the introductory part of thisspecification. In the prior art electromagnetic clutch, a cylindricalcover member 180 is secured to a rotatable body 112 in such manner thata flared portion 184 extending substantially radially outwardly from anaxial end of a peripheral wall 182 of the cover member is clamped by andbetween an axial end of a bearing 124 and a shoulder 140 on an innerperipheral wall 114 of the rotatable body 112. Thereafter, a snap ring132 is caused to pass through an opening 188 defined by an annular endwall 186 of the cylindrical cover member 180 toward the bearing 124 andthen is snapped into or fitted in an annular groove 134.

In the prior art electromagnetic clutch shown in FIG. 2, the opening 188defined by the annular end wall 186 of the cylindrical cover member 180is required to have a diameter of size sufficient to allow the snap ring132 to pass through the opening 188. This makes it impossible toincrease the radial length hp of the annular end wall 186, so that areservoir for oil and grease defined by the peripheral wall 182 and theannular end wall 186 cannot be increased in volume. In addition, if thebearing 124 has its reduced radial dimension betweeen its inner andouter peripheral surfaces, it is troublesome and difficult to fit thesnap ring 132 into the groove 134, because the cylindrical cover memberis previously installed.

What we claim is:
 1. An electromagnetic clutch for respectivelyconnecting and disconnecting a drive source to and from a driven devicehaving a fixed hollow cylindrical projection and a rotatable shaftextending within said hollow projection in concentric relation thereto,said electromagnetic clutch comprising:a rotatable body made ofmagnetizable material and disposed around said hollow cylindricalprojection of said driven device in concentric relation thereto, saidrotatable body being drivingly connectable to said drive source forrotation around an axis of said shaft and having an inner peripheralsurface faced to said cylindrical projection and opposite axial endfaces; a bearing disposed between an outer peripheral surface of saidcylindrical projection and the inner peripheral surface of saidrotatable body for rotatably supporting said rotatable body on saidcylindrical projection; an annular armature made of magnetizablematerial and connectable to said shaft of said driven device forrotation therewith, said armature being faced to one of the oppositeaxial end faces of said rotatable body, but normally spaced therefrom bya suitable gap, said armature being movable between an engaging positionwhere said armature is attracted and abuts against said one axial endface of said rotatable body to allow the rotation of said rotatable bodyby said drive source to be transmitted to said shaft and a disengagingposition where said armature is spaced from said one axial end face ofsaid rotatable body by said suitable gap to prevent the rotation of saidrotatable body from being transmitted to said shaft; an excitingsolenoid associated with said armature for moving the same between saidengaging and disengaging position in response to energization anddeenergization of said solenoid; and a cylindrical cover member made ofthermoplastic material and fixedly mounted, independently of saidbearing, on a portion of the inner peripheral surface of said rotatablebody between said one axial end face thereof and said bearing, saidcover member having a cylindrical peripheral wall having an axial lengththereof extending so as to cover said gap between said one axial endface of said rotatable body and said annular armature and also cover aninner peripheral surface of said annular armature, said cylindricalcover further having an annular end wall radially inwardly extendingfrom one axial end of said peripheral wall of said cylindrical covermember remote from said bearing, to a location where an opening definedby an inner peripheral edge of said annular end wall is located adjacentto a free end of said hollow cylindrical projection of said drivendevice, said peripheral wall and said annular end wall of said covermember cooperating with each other to define a reservoir space having arelatively large volume for oil leaking out of said driven device andgrease flowing from said bearing.
 2. An electromagnetic clutch definedin claim 1, further comprising connecting means for connecting saidarmature and said shaft of said driven device to each other so as toallow said armature to be rotated with said shaft and also allow saidarmature to move toward and away from said one axial end face of saidrotatable body relative to said shaft.
 3. An electromagnetic clutchdefined in claim 2, wherein said one axial end face of said rotatablebody is located adjacent to a free end of said shaft of said drivedevice, said connecting means including a hub fixedly connected to saidfree end of said shaft and a resilient member disposed between andsecured to said hub and said armature.
 4. An electromagnetic clutchdefined in claim 3, wherein said hub has a cup-shaped body portion and ahollow projecting portion axially extending from a bottom of saidcup-shaped body portion, said free end of said shaft extending into saidhollow projecting portion, said annular end wall of said cylindricalcover member extending to a location closely adjacent to the outerperipheral surface of said hollow projecting portion.
 5. Anelectromagnetic clutch defined in claim 4, wherein said resilient memberis a rubber ring secured to peripheral surface of said cup-shaped bodyportion.
 6. An electromagnetic clutch defined in any one of claims 1-5,wherein said rotatable body has an annular groove formed in a portion ofthe inner peripheral surface thereof between said bearing and said oneaxial end face, said cylindrical cover member having at least oneprojection extending radially outwardly from the opposite axial end ofsaid peripheral wall of said cylindrical cover member, said at least oneprojection being frictionally fitted into said annular groove.
 7. Anelectromagnetic clutch defined in claim 6, wherein said at least oneprojection on the opposite axial end of said peripheral wall of saidcylindrical cover member extends circumferentially continuously.
 8. Anelectromagnetic clutch defined in claim 7, wherein said cylindricalcover member is made of material having resiliency.
 9. Anelectromagnetic clutch defined in claim 8, wherein said cylindricalcover member is made of 66-nylon.
 10. An electromagnetic clutch definedin any one of claims 1-5, wherein said rotatable body has therein aconcentric recess, said solenoid being annular and disposed in saidconcentric recess in concentric relation thereto.
 11. An electromagneticclutch for respectively connecting and disconnecting a drive source toand from a driven device having a fixed hollow cylindrical projectionand a rotatable shaft extending within said hollow projection inconcentric relation thereto, said electromagnetic clutch comprising:arotatable body made of magnetizable material and disposed around saidhollow cylindrical projection of said driven device in concentricrelation thereto, said rotatable body being drivingly connectable tosaid drive source for rotation around an axis of said shaft and havingan inner peripheral surface facing said cylindrical projection andopposite axial end faces; a bearing disposed between an outer peripheralsurface of said cylindrical projection and the inner peripheral surfaceof said rotatable body for rotatably supporting said rotatable body onsaid cylindrical projection; an annular armature made of magnetizablematerial and connectable to said shaft of said driven device forrotation therewith, said armature being faced to one of the oppositeaxial end faces of said rotatable body, but normally spaced therefrom bya suitable gap, said armature being movable between an engaging positionwhere said armature is attracted and abuts against said one axial endface of said rotatable body to allow the rotation of said rotatable bodyby said drive source to be transmitted to said shaft and a disengagingposition where said armature is spaced from said one axial end face ofsaid rotatable body by said suitable gap to prevent the rotation of saidrotatable body from being transmitted to said shaft; an excitingsolenoid associated with said armature for moving the same between saidengaging and disengaging position in response to energization anddeenergization of said solenoid; and a cylindrical cover member made ofthermoplastic material and disposed in concentric relation to saidhollow cylindrical projection of said driven device, said cover memberhaving a cylindrical peripheral wall having one axial end thereofadjacent to said bearing and the other axial end remote therefrom, saidone axial end of said peripheral wall being fixedly mounted,independently of said bearing, on a portion of the inner peripheralsurface of said rotatable body between said one axial end face thereofand said bearing, said peripheral wall having an axial length thereofextending so as to cover said gap between said one axial end face ofsaid rotatable body and said annular armature and also cover an innerperipheral surface of said annular armature, said cover member furtherhaving an annular end wall extending radially inwardly from said otheraxial end of said peripheral wall to a location where an opening definedby an inner peripheral edge of said annular end wall is located adjacentto a free end of said hollow cylindrical projection of said drivendevice, said peripheral wall and said annular end wall of said covermember cooperating with each other to define a reservoir space having arelatively large volume for oil leaking out of said driven device andgrease flowing from said bearing.